This invention is particularly suitable for use with heat exchanger assemblies of the type having a heat transfer core including a plurality of fins in parallel stacked relationship for defining heat transfer surfaces and a plurality of fluid-carrying tubes extending transversely through the fins for defining a fluid circuit. Heat exchanger assemblies of this type are frequently used in the automotive industry as oil coolers, air heaters, radiators and in air-conditioning systems.
It is necessary to connect various tubes together in assembling such heat exchangers. It has been conventional to join tubes in such an assembly by being fluxed and soldered. The soldering of the joints requires significant heat energy, special handling of the components and the soldering materials and, in addition, frequently produces undesirable fumes. In order to overcome some of the problems associated with soldered joints, applicant developed a solderless joint for joining two tubes together by forming one tube with a frustoconical tapered portion extending to a shoulder and another tube with an outwardly flared portion and inserting the frustoconical portion into the flared portion and crimping or bending the end of the flared portion over the shoulder. Such a joint is disclosed in applicant's U.S. Pat. No. 4,172,496 granted Oct. 30, 1979. That joint has proved to be very effective in heat exchangers having a limited number of rows of tubes so that the crimping operation is accomplished by tools which move radially with respect to the axis of the two tubes being joined together. Such a crimping operation is necessary because the heat exchangers typically include a U-shaped tube or return bend for interconnecting adjacent tubes extending through the heat exchanger core and the crimping tools must pass under and clear the U-shaped return bend. In forming such a joint the lengths of the flared portions are not easily maintained constant and, therefore, to prevent the necessity of sizing the lengths of the flared portions, the flared portions are allowed to gather in being crimped about the shoulder. However, there are heat exchanger assemblies having a multiplicity of rows of tubes which must be interconnected by U-shaped return tubes wherein the crimping operation must be accomplished by crimping tools moving axially of the tubes at the joint and such will not permit the gathering of the material crimped over the shoulder of the joint.